Event vertex and time reconstruction in large-volume liquid scintillator detectors

Abstract

Large volume liquid scintillator detectors with ultra-low background levels have been wildly used to study neutrino physics and search for dark matter. Event vertex and event start time is not only useful for event selection, but also essential for reconstruction of event energy. In this paper, a set of event vertex and event time reconstruction algorithms using charge and time information collected by photomultiplier tubes are comprehensively studied. The impact of photomultiplier tubes properties is also investigated. The results show that transit time spread is the main effect that worsens the vertex reconstruction, while the influence of dark noise is limited. In addition, when the event is close to the detector boundary, charge information provides better performance for vertex reconstruction than time information.

Radioactivity control strategy for the JUNO detector

“…These waveforms are processed by PMT calibration algorithm and CalibEvent objects are saved. The event reconstruction algorithm [37][38][39] performs the event reconstruction by reading CalibEvent objects and stores RecEvent objects. At last, physicists can perform any physics analysis from RecEvent objects.…”

Improving the machine learning based vertex reconstruction for large liquid scintillator detectors with multiple types of PMTs

“…In the traditional method of the vertex reconstruction from Ref. [12], the two types of PMTs are handled separately with different residual time PDFs due to different TTS. Following the same strategy, the FHT information should be separated into two images (or channels), one for each type of PMTs.…”

“…Ref. [12] also showed that the charge distribution of all the PMTs is sensitive to the vertex of the positron, especially near the detector boundary. A novel method [13] based on machine learning was applied to JUNO reconstruction as well.…”

“…As the positron energy increases it behaves more and more like a point source. Previously a maximum likelihood method [12] was developed to reconstruct the vertex of positrons-the energy deposition center to be more precise using mainly the time information of the first photon hit of photo-multiplier tubes (PMTs) together with the scintillation timing profile of LS. Ref.…”

Low Radioactive Material Screening and Background Control for the PandaX-4T Experiment

“…Beyond the standard model, Weakly Interacting Massive Particle (WIMP) is a competitive candidate for DM. Currently, dual-phase xenon detectors are leading in the search for WIMPs in a mass range from a few GeV/c 2 to several TeV/c 2 [2][3][4]. PandaX collaboration has constructed a series of dual-phase xenon time projection chambers (TPCs) to search for WIMP at the China Jinping underground laboratory (CJPL) [5].…”